There is a growing need for a flat-panel display for use in a computer with a wide spreading use of information terminals. With further advancement of informatization, there are also increasing opportunities in which information, which has been conventionally provided by paper medium, is digitized. Particularly, the needs for an electronic paper or a digital paper have been recently increasing since they are thin and light weight mobile display media which can be easily held and carried (see Patent document 1, described below).
Generally, the display medium of a flat panel display device is formed by using an element such as a liquid crystal, an organic EL (organic electroluminescence) and an electrophoresis. In such display medium, a technology which uses an active drive element (TFT element) as an image drive element has become a mainstream to ensure a uniformity of the screen luminosity and a screen rewriting speed and so forth. For example, in the conventional display device for use in the computer, TFT elements are formed on a substrate wherein the liquid crystal element, the organic EL element or the like is sealed.
As a TFT element, semiconductors including a-Si (amorphous silicon) and p-Si (polysilicon) can be mainly used. These Si semiconductors as well as metal materials used for electrodes and wirings are subjected to a multilayering process wherein each of a source electrode, a drain electrode and a gate electrode is sequentially stacked on the substrate, which leads to an achievement of the production of the TFT element.